Aircraft noise reduction is an ongoing concern at airports around the world, as air traffic continues to increase and as people living near airports, or along aircraft take-off and landing flight paths, express concerns about aircraft noise. Accordingly, most airport facilities have regulations that set noise limits and that control aircraft flight paths on take off and landing. Some airport facilities now provide financial incentives or restrict terminal privileges to encourage airlines to reduce noise even further.
Aircraft noise has several sources, for example engine noise, landing gear orientation upon take off and landing, aircraft aerodynamic effects, among others. Accordingly, noise abatement is a complex issue. A strategy for addressing aircraft noise reduction is to consider each component of the aircraft, such as engine, landing gear, wings, etc., separately to make component-specific determinations. Consideration should also be given to other factors that may limit component-specific attenuation efforts, such as safety considerations. For example, reducing engine speed may reduce engine noise, but may be hazardous when an aircraft is fully loaded, taking off from a higher altitude airport under hot weather conditions. Certain airports may have relatively short runways for take off, necessitating high engine loads which result in higher noise levels.
The engine is one of the major noise generators on an aircraft. Much effort has been devoted to engine noise reduction. Newer engine designs may produce less noise than older but still useful engines. With so many aircraft already in service, and with such a high investment in existing engines that have a long useful life span, routine engine replacement for lower levels of sound generation may not be commercially feasible.
One of the sources of engine noise is the engine nacelle inlet area. To reduce noise in the nacelle inlet area, an acoustic panel is deployed as a lining at the nacelle air inlet. The acoustic panel is comprised of two separate acoustic panel halves that are joined at their ends to form a hoop shape that approximates the nacelle inlet shape. These acoustic panels have “non-acoustically treated” areas that are necessary to provide strengthened attachment points for the panel halves to the nacelle inlet. The non-acoustically treated areas do not, therefore, provide noise attenuation like the other areas of the panels. In addition, fastening the panel halves in place requires a splice fitting that has a plurality of fasteners extending through it. These fasteners create discontinuities in the otherwise smooth surface at the nacelle inlet thereby presenting a further source of noise at the nacelle inlet.
Accordingly, it is desirable to develop an acoustically-treated nacelle inlet panel for aircraft noise reduction. In addition, it is desirable that the panel be monolithic or “single piece” to reduce the need for a splice fitting with exposed fasteners projecting into the nacelle air inlet. It is also desirable that the panel be free of areas that are not acoustically treated. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.